Automatic dialling device

ABSTRACT

Automatic dialing device for dial telephones comprising a rotor, means for driving said rotor for one turn and an arrangement of cam discs provided with notches and blades for reading out said cam discs so devised that the waveform of the generated dial pulses does not depend upon the shape of the notches. The cam discs comprise a toothed track with rectangular notches indexed in its periphery and a smooth track having a diameter slightly smaller than the toothed track and adjacent thereto and accurately coaxial therewith, and first blades and second readout blades substantially parallel to each other are provided, each first blade resting on the smooth track and each second read-out blade terminating in an inclined portion provided with a tooth extension having a width lesser than the blade width, the edge of the inclined portion of said second blade engaging the notches of the toothed track in the radial plane passing through the contact point of the first blade and smooth track and the edge of the tooth extension resting on the first blade in the said radial plane when the edge of the inclined portion falls into a notch.

United States Patent Jean-Pierre Nicolas Nice, France [72] Inventor [21] Appl. No. 697,683

[22] Filed Jan. 15, 1968 [45] Patented Feb. 23, 1971 [73] Assignee Societe Le Prototype Industriel Nice, France [32] Priority Jan. 17, 1967 [33] France [54] AUTOMATIC DIALLING DEVICE 3 Claims, 13 Drawing Figs.

FOREIGN PATENTS 1,162,880 9/1962 Germany 633,201 2/1962 Italy ABSTRACT: Automatic dialing device for dial telephones comprising a rotor, means for driving said rotor for one turn and an arrangement of cam discs provided with notches and blades for reading out said cam discs so devised that the waveform of the generated dial pulses does not depend upon the shape of the notches. The cam discs comprise a toothed track with rectangular notches indexed in its periphery and a smooth track having a diameter slightly smaller than the toothed track and adjacent thereto and accurately coaxial therewith, and first blades and second read-out blades substantially parallel to each other are provided, each first blade resting on the smooth track and each second read-out blade terminating in an inclined portion provided with a tooth extension having a width lesser than the blade width, the edge of the inclined portion of said second blade engaging the notches of the toothed track in the radial plane passing through the contact point of the first blade and smooth track and the edge of the tooth extension resting on the first blade in the said radial plane when the edge of the inclined portion falls into a notch.

PATENTEU mes m v SHEET 2 BF 5 m AVE INVENTOR:

Jean-Pierre NICOLAS PATENTEUFEBNIBYI f 3, 566Q O4'3 saw u or 5 INVENTOR Jean-Pierre NILAS AUTOMATIC DIALLING DEVICE This invention relates to an automatic telephone dialing device to be associated with a conventional telephone of the dial type and, more particularly, to a device of this kind in which the called subscribers numbers to be automatically dialed are represented by group of notches cut into the periphery of a motor driven cam or disc which operate a normally open switch to supply momentary electrical impulses.

The principal difficulty encountered in the devices of this kind is due to the fact that the periphery of the disc whose diameter is equal to the diameter of a telephone dial or slightly larger must be embossed to embody all the digits of a call number which may comprise as much as ten decimal digits. It results that the sectoral angle of the disc available to store digit 1 is no more of about 30 as in the conventional dials, but only of about 3 and in these conditions it is quite difficult to obtain, through a mechanical sensing member operated by the embossing and acting on a contact, dialing pulses of the required waveform.

In a first kind of automatic dialing facilities, the pulses produced by the sensing member actuated by the cam are not directly used as dialing pulses but instead as gating pulses for a precision call pulse generator. The storage disc only comprises embossments having a sectoral length proportional to the number of pulses to be transmitted. At a read-out stationary place, each projection of the disc lifts up the mobile blade of a first switch, thereby opening a contact which in its rest position is closed and short circuits the pulse generator. The pulse generator is for example of the rotating cam type and is continuously rotating and acting upon a second switch. Every time the second switch opens, the line receives a number of pulses, the number depending solely upon the developed length of the protuberance which opened the first switch. A disadvantage of this first kind of facility is the need for very high mechanical accuracy to ensure the necessary synchronism between, on the one hand, the times at which the leading edges of the protuberances of each storage disc pass by the sensing member and, on the other hand, the times at which the pulses transmitted continuously by the transmitter are allowed through. Equipment of this kind is therefore expensive and mechanical wear may cause it to go out of adjustment. Another disadvantage is the need for accuracy in cutting the protuberances and in devising the means for centering and securing the discs; since the discs are works-made items, the user must contact the maker whenever he wants to change all or some of his call list.

In a particular type of this class of dialing devices, the dialing pulse transmitter is the telephone dial proper which is allowed to rotate by increments of 30 in the clockwise direction under the control of the pulses generated by the memory-cam and then is released in counterclockwise rotation and thus produces suitably shaped dialing pulses,

ln a second known kind of facilities, the projecting parts of the storage disc are usually embodied by teeth each allotted to the transmission of a pulse, so that every digit of the called' number corresponds to a series of consecutive teeth, followed by a space of appropriate length. This feature obviates the difficulties hereinbefore mentioned in synchronizing the disc and the transmitter since the disc is the pulse transmitter proper, but another difficulty occurs, using a relatively small-diameter storage disc, to obtain a large number of pulses which are of appropriate shape and which are stablein time. The difficulty becomes even greater if it is also required that the user can himself compile the storage disc. The reason is that, the number of pulses of a complete call number being in practice very large, the tooth width is bound to be less than 1 mm for the conventional disc diameter and yet so small a tooth must ensure compliance with the telecommunication standards which relate the dial pulse duration to the duration of the interval between pulses or guard interval. For example in the case where the pulse duration is two times the guard interval,

that is the ratio of the break time of the switch to the make time is theoretically two, this ratio must practically be somewhere between 1.7 and 2.2.

There are three kinds of device in this second category.

In the first kind of device, each tooth acts by just one of its fronts to trigger the transmission of a pulse by an electronic monostable having an adjustable flip-flop time. This solution has theoretical interest, enabling as it does the tooth density on the disc periphery to be increased, but has the disadvantage of requiring bulky and expensive electronic means.

In the second kind of device, each tooth raises at the sensing station a flexible strip associated with a stationary strip, to open a contact while the tooth passes by. A practical disadvantage of such devices is wide fluctuations in the ration of break time to make time, first due to even slight eccentricity of the disc relatively to its axis, second due to the thickness of the sensing member relatively to tooth width, so that the sensing element can provide only a rough analysis of the relief formed by the teeth, and thirdly due to the irregularity of the teeth shape.

It is an object of this invention to provide a facility of the kind set forth at the beginning hereof and mainly comprising a rotor bearing storage discs having a toothed peripheral track, each disc being adapted to be set up by the user for a particular called number and of being assembled or disassembled by the user, self-locking levers respectively associated with the discs so that the same can be operated selectively, means for driving the rotor, means for transmitting pulse trains in dependence upon the relief of the particular disc operated, and switchable means for combining the action of the rotor-driv' ing means with the pulse-train-transmitting means, this facility being substantially free from the difficulties hereinbefore set forth.

To this end, according to a first feature of the invention, a single storage disc made entirely of insulant corresponds to each called or directory number stored in the facility and has a toothed track over only approximately one-half of its thickness, the other half of its thickness having a smooth track which is coaxial of and slightly recessed from the toothed track over approximately the height of the teeth, the smooth track having resting on it a first associated tine of a conductive comb, hereinafter called the bottom comb, whereas a second associated tine of a conductive comb, hereinafter called the top comb, the top comb being insulated from the bottom comb, when operated by the associated lever follows the relief of the toothed track so that pulse trains are transmitted as a result of the intermittent contact between the first tine and the second tine.

An advantage of this system is that a half-disc can by construction be centered satisfactorily relatively to the other half.

According to a second feature of the invention, to obviate all possible irregularities arising from the means for driving the rotor, the same being formed by a motor and reducer set, the rotor-driving means take the form of a gearwheel and worm, the gearwheel being rigidly secured to the disc shaft and having the same number of teeth as the storage discs would have if not slotted, so that one revolution of the motor corresponds to one transmitted pulse and the duration thereof is therefore independent of drive cycle irregularities.

According to a further feature of the invention, the switch means comprise a plain lever operated by the means for locking the lever associated with the storage discs, the lever of the switch means acting when in operation to substitute the contact of the automatic dialing device for the contact of the dial of the telephone set and to close the switch of the motor supply circuit, and being returned to the normal state by a projection of a stick cam wheel at the end of a cycle corresponding to one revolution of the rotor.

This feature on its own might have the disadvantage for the user of him being usable to recover the telephone line (use in conversation) only at the end of the cycle corresponding to a complete revolution of the rotor; in the case of a directory number which is short in relation to disc capacity, the called subscriber might have hung up before the calling subscriber begins to speak.

To obviate this disadvantage, according to another feature of the invention, each storage disc has lateral studs which are at a given distance from the disc shaft and which can be broken as required so that one of the remaining studs cooperates with the associated lever to return the same automatically to its normal position and restore line availability to the user upon completion of dialing of the number without preventing the motor from finishing its cycle.

According to a further feature of the invention, in cases in which a single disc may bear the national or international toll call number as well as the office and directory number of the correspondent, an extra stud is provided in a particular position of each disc and cooperates with the associated lever, while the rotor cam disc has appropriate means for temporarily interrupting completion of the motor cycle.

According to still a further feature of the invention, the rotor can be embodied either by a stack of indentical members of revolution of appropriate shape or as a single member formed by moulding of a plastics and moulding from a casting on a metal spindle which stays bare at the journals, the rotor being formed in any case with asymmetrical grooves ensuring that the discs are positioned correctly.

The facility embodied by the various features hereinbefore set forth have the general advantage of simplicity and therefore of low cost.

These and other features and advantages of the invention will become clearer from the following detailed description of a preferred but nonlimited form of the facility according to the invention reference being made to the accompanying drawings, wherein: 4

FIGS. la and 1b are perspective views of the facility without cover and with cover, respectively;

FIGS. 2a and 2b are views, in diagrammatical longitudinal section and in end elevation from the motor end respectively, of the rotor without discs and without drive gear;

FIGS. 3a, 3b and 3c are respectively two views, in side elevation and end-on of a storage disc and a detail section of a stud of the disc;

FIGS. 4a and 4b are views in side elevation of a disc lever in the raised or inoperative position and in the lowered or operative position respectively; 1

FIG. 5 is an exploded perspective view of two metal combs and their insulating or securing means;

FIG. 6 is an end view of the facility at the motor end, and

FIGS. 7a and 7b are circuit diagrams for the facility when the same is in its rest position and in its operative position, respectively.

Referring to FIGS. 1a and lb, the facility comprises a frame 1 which is in shape substantially parallelepipedic and which has inter alia two sideplates lll, II, a bottom frame or plinth 12 in which a releasable bottom member 12a is received between the end plates 11, 11 and which extends beyond the end plate 11 as a portion 12b, and a cover whose top part comprises pushbuttons 13a, 13b having a function which will be described hereinafter.

Referring now to FIGS. 2a and 2b, a rotor 2 is rotatably mounted in the plates 11 and ill and takes the form of a shaft 21 on which a number of identical members 22 of revolution are stacked coaxially and keyed. Three of the members 22 which are fairly far apart from one another are extended in the same radial direction by trapezia whose minor bases enable a rod 23, which in shape is cylindrical but with a facet 23a, to be secured to the rotor 2 parallel to the shaft 21, e.g. by screws. The rotor 2 bears outside the end plate 11 a cam disc 24 which is driven by a dog extending from the rod 23; the disc 24 has a cylindrical projection 24a extending from its outer surface. Also mounted on the rotor 2 is a rotor-driving gearwheel 25 which is rigidly secured to the shaft 21, e.g. through the agency of a nut cooperating with a screw-threaded part of the shaft 21. As can be gathered from the view in FIG. 2b from the cam end but with the gearwheel 25 removed, the rotor assembly can be embodied if required-except for the wheel 23-as a single item by moulding of a plastics in shells and casting from a moulding on a metal shaft or spindle 26 which is bare in the region of its ends or journals 26a, 26a and in the region of the part to which the wheel 25 is secured.

The cam 24 is formed on its periphery with two notches 24b, 240 which can be contrived in moulding; the notch 24b is the normal notch and the notch 240 is the toll number notch.

The members 22 on the shaft 21 are so shaped that between two consecutive members 22 there is a cylindrical groove bounded by two surfaces of revolution which are asymmetrical in respect of one another; for instance, one such surface can be a plane surface perpendicular to the shaft 21 and the other such surface can be conical.

As can be seen in FIGS. 3a and 3b, a storage disc 3 made of an insulating material, preferably a plastics, can be threaded into each rotor groove. Each storage disc 3, which has a diameter e.g. of approximately 70 mm, has in known manner- -but over only one-half of its thickness-a regular sequencewhen the disc is brandnewof rectangular teeth 31 separated from one another by spaces 32 and of a length of e.g. approximately 1.5 mm. The teeth 31 can be broken so that the user can permanently form on the disc the directory number of a particular correspondent. On the other half of its thickness each disc 3 has a plain cylindrical coaxial track which is slightly recessed, e.g. by 2 mm, from the tooth tips. The front surface of each disc 3, such surface being the surface near the toothed part, also has a number of studs or pins or the like 33 which are arranged laterally on generatrices of an imaginary coaxial cylinder of a diameter e.g. of approximately 50 mm and which project slightly outwards, e.g. by approximately 3 mm. At the base of each pin 33 the disc-forming material is recessed funnel-fashion, as can be seen in FIG. 30, so that a stud 33 can be removed just by breaking.

Each disc 3 also formed with a radial slot 34 whose width corresponds to the internal diameter of the grooves of rotor 2 and which flares slightly outwards, the edges of the slots 34 being slightly chamfered and being formed with two coaxial circle-arc recesses 34a. Another slot 35 offset slightly from the slot 34 cooperates therewith to bound a tongue or strip or the like 36 which is resilient. The recesses 34a cooperate with the rod 23 to ensure that each disc is securely located on the rotor and is centered relatively to the geometric axis of the rotor. Each disc 3 is formed with an aperture 37 for its removal. Since the surfaces bounding each groove are asymmetrical, as already mentioned, eachdisc cannot but be inserted the right way round.

Referring now to FIGS. 4a and 4b, each disc 3 has associated with it a flat lever 4 rotatably mounted at one end by way of a recess 41 engaged on a longitudinal spindle 41a connected to the frame as to be pivotable in a plane perpendicular to the rotor at a very reduced distance from the toothed surface of the associated disc 3, between a raised rest position and a lowered operative position. As can be seen in FIG. la, each lever 4 is received with clearance in a slot 14a in a sidewall member 14 of the frame. Each lever 4 is formed on its bottom edge with a slight recess 42 prolonged by a triangular tooth 43 whose leading surface has an appropriate radius of curvature and acts as a ramp to raise the lever, the trailing surface of the tooth 43 being perpendicular to the lever axis. When the lever 4 is in the raised position, therefore, the pins 33 are free to pass below the tooth 43, but when the lever 4 is in its bottom position, the pins 33 return the lever 4 to its stop position. The outer edge of each lever 4 is formed, at a reduced distance from its pivoting end, with a recess 44 in which a spring strip serving as return spring, to be described hereinafter, engages. The free end of each lever 4 takes the form of a triangular nose or beak 45.

All the levers t are aligned so that any of them can cooperate by way of its end 35 with a longitudinal, e.g. cylindrical, rod 3, which rotates with reduced friction in the frame end uprights I, II and which is formed with a dihedral recess 51 whose cross section extends as far as the geometric axis of the rod 5 and matches the shape of the lever noses 45. Each lever 4 can be lowered into the operative position by means of an associated pushbutton in the cover. As it descends, the operated lever 4 pivots the bar 5, which through the agency of .its recess 51 locks the selected lever 4 and, having pivoted,

prevents the lowering of any other lever d.

As can be seen in FlGS. la, 6, 7a and 7b, the corresponding end of the rod 5 has on it, beyond the upright 11, a cam 52 comprising three radial fingers 53-whose free end has a convex V-shape-fid, 55, and, freely rotatable on the end of the rod 5, a bellcrank lever 56having two arms 56a, 56b.

As can be seen in FIGS. in and 6, a flat lever 6 is so articulated at one end by way of a recess 61 engaged on a longitudinal spindle 61a connected to the frame as to be pivotable in its plane, parallel to and outside the end plate 11, between a raised rest position and a lowered operative position. The lever 6 bears laterally a first pin or stud 62 which cooperates with the spindle 61a to retain a return spring 620, for instance, a horseshoe strip, and a second pin 63 whose purpose will be described hereinafter. The bottom edge of the lever 6 is formed with a asymmetrical triangular tooth 64 adapted to cooperate with the cam projection 24a. At its free end the lever 6 is formed with a concave-V recess adapted to cooperate with the convex-V end of the finger 53.

Preferably, all the items hereinbefore described are made of water-repellant plastics having high dimensional stability, and the storage discs are made of brittle plastics.

A description will now be given of the electrical part of the system which, as can be seen in FIG. 5, comprises two combs made of a conductive metal, for instance, of chrysocale" alloya bottom comb 71 and a top comb 75. In the bottom comb 711, relatively narrow and long tines 73 and relatively the plain 74 extend from a longitudinal base member 72. The long tines '73 are stationary and substantially horizontal and rest tangentially on the plain tracks of the discs 3, whereas the short tines 74 form the return springs for the levers 4 and therefore each engage in the recess 44 in the particular lever 4 concerned. in the top comb 75, relatively wide tines 77 extend from a longitudinal base member 76. These tines are of a uniform kind and each terminates at the free end in a nose portion 78 descending at 45 and having at one of its side terminations a projecting rectangular tooth 78a perpendicular to the tine plane. The edge of the nose portion and the edge to the tooth portion are in a single and same plane perpendicular to the tine plane. Each tooth 78a contacts the associated tine 73 in the absence of teeth on the toothed track or in the space between two consecutive teeth, when the lever 4 is in its bottom operative position. v

The base members 72, 76 and an insulating rod 70 therebetween are appropriately pierced with apertures which register with one another so that the comb base members 72, 76 can be secured to one another and to the sidewall member 14 of the frame by means of self-tapping metal screws 14b.

As can be seen in FIGS. 6, 7a and 7b, aselector relay 81 has four strips 81a, 81b, 81c, 81d which have contact tips and which are electrically connected to the telephone set served, more particularly to the terminal strip thereof, the strips 81a,

81b, 81c being connected to the handset while the strips 81c,

81d are connected to the tines 73, 77 which form the dial pulse transmission contacts of the facility.

When in the operative (transmitting) position, the lever 6 is lowered to rotate the cam 52, the finger 54 retracts upwards, and the finger 55 interconnects the strips 81a, 81b, 81c and leaves the strips 81c, 81d apart from one another.

in the normal position (handset in use), the lever 6 is raised, the finger 54 separates the strip 81a, 81b, 810 from one another, and the strips 81c, 810 are connected together. The bellcranlt lever 56, whose arm 56a is operated by the extra pushbutton 13b of the cover, acts by way of its arm 56b to operate the switch 81 by action on the strip 81c, the same having for this purpose a projection (not shown) at right-angles in its plane.

To rotate the rotor 2, the gear 25, which has the same number of teeth as the number of teeth on a brand new storage disc assumed not to be slotted, cooperates with a worm 91 rigidly secured to the shaft of a synchronous motor 92 supplied from the AC mains via a microswitch 93. The same has two contact strips 93a, 93b which have their free ends curved so that the strip 930 can operate with the pin 63 of the lever 6 and the strip 93b with the two recesses 2%, 240 in the rotor cam 24. The whole is so devised that the switch 93 is opened when the strip 93a is raised by the pin 63 of the lever 6 and, simultaneously, the strip 93b is lowered by a cam recess 24b or 24c, and the switch 33 is closed in all other cases.

A visual telltale in the form of a neon tube 94 lights up when the motor 92 is energized.

The facility operates as follows:

In a preparatory phase, the user makes a list of the selected correspondents and of their ofiice and directory numbers. The user then prepares one storage disc per correspondent. In the facility constructed, each storage disc has the number of teeth required to dial" the longest possible eight-digit number- -i.e., 136 teethin the operative part of its periphery (outside the slot), a FIG. corresponding to approximately 142 teeth over the full periphery of an unslotted disc. However, the tooth number is not limited to this value and, more particularly, could be increased for call numbers containing more than eight digits. However, call numbers are seldom of such length and a single disc can usually be used to record the two national toll digits or the two international digits as well as the eight digits of the chosen correspondent.

After the number of the chosen correspondent has been set up, the user determines the or each pin which should be broken to ensure that the disc restores the line as soon as possible.

In the facility constructed, each disc has eight pins 33 whose positions correspond to teeth having approximately the following ranks respectively: 24 for all the two-digit numbers between 11 and 19 60-80-90-100-1l0-120-130-i.e, 10-tooth steps-for the various directory numbers in accordance with their length.

The user repeats the same operation for the various correspondents on his list, to the limit of the capacity of the facility (20 discs in the facility constructed).

For greater convenience, the user writes the name of the correspondent on each disc. He places the discs on the rotor in the order of his list, passing them through the aperture in the base of the apparatus, each into the first available groove of the rotor, until it engages with the centering rod 23. The user then connects the device by the connecting means provided to the mains and to the telephone station to be served.

The following different cases may arise in practical use.

For a local call the user offhooks and, having obtained the dialling tone, presses the pushbutton 13a corresponding to the required called subscriber. This action depresses the associated lever 4 against the force of the spring 74, the lever 4 locking itself and acting by its nose 45 to pivot the rod 5. The change in the position of the rod 5 causes a change in the position of the cam 52, the fingers 54, 55 rotating so as to open the contact 8lc-8ld and interconnect the strips 81a, 81b, 81c, while the finger 53 of the cam 52 lowers-the lever 6 into the operative position. the opening of the contact 8lc-8ld results in the substitution of the contact 7377 for the contact of the conventional dial of the telephone set. Since the pin 63 of the lever 6 descends, the switch 93 closes and the motor 92 starts. Independently of the presence of the recesses 24b, 24c the rotor starts to make a complete revolution In the projection of the strip 93b disengages from the recess 24b in the cam 24. In connection with the disc 3 whose lever 4 has been operated, the tine 73 of the bottom comb slides over the plain track of the disc whereas the edge of the inclined portion 78 of tine 77 of the top comb follows the relief of the rectangular teeth of the track of the disc. When this edge falls into a notch, the edge of tooth 78a contacts blade 73 which closes the loop of the subscribers line. Thus pulse trains corresponding to the telephone number of the called subscriber as represented by the disc teeth are sent on the line. Upon the completion of this operation, a pin 33 appears and returns the lever d and rod to the normal state; consequently, the cam 52 rotates in the opposite direction and its fingers so rotate that the finger 5d opens the loop 81c, lillb, 81c and closes the loop file, 3112, so that the handset can be used as usual while the finger 52 raises the lever 45 back into its normal position. The user now has line availability while the rotor completes its one-revolution rotation until the end of the strip 931; reengages in the cam recess 2 th. if no pin 33 of the particular disc 3 concerned should cause a return to normal, such a return would be produced by the projection 2 in or cam 24 cooperating with the tooth 6d of the lever d at the end of the revolution of the cam, at the time when the end of the strip 93b reengages in the cam recess 24b. This case occurs when the called subscribers number is so long that all the pins have had to be broken. The motor 93 stops in both cases.

in the case of a toll national or international call, assuming first that one of the discs is reserved for a two-digit number, so that the next eight digits are recorded on some other disc, the user starts as in the previous case by first pressing the button 11% corresponding to the two-digit toll call sign. Having obtained the second calling tone and when the telltale 9d has gone out, he presses the button 13a corresponding to the called subscribers office and directory number and proceeds as previously.

in the case of a toll national or international call, on the assumption now that the two-digit toll call sign has been recorded on the same disc as the required subscribers telephone number, the user, as previously, merely presses the button 130 corresponding to the called subscribers disc. The operation of the rotor 2 first initiates transmission of the toll call sign, whereafter the special pin 33 of the disc relative to the two-digit numbers returns the system 5, 8i, 6 to the normal state, so that the motor 9?: stops when the end of the strip @Bb engages in the cam recess 24c. After the special dialling tone has been obtained, the user presses the same button 113a again and proceeds as in the previous cases.

It is to be noticed that the arrangement of tracks and blades which has been disclosed allows call pulses of exact duration to be obtained without the disc notches having an accurately rectangular shape. As a matter of fact:

ithe smooth track and the toothed track of the disc are exactly equidistant;

ii blade 73 is tangent to the smooth track and the edge of the inclined portion 78 contacts the toothed track in the same transverse radial plane of the disc and this plane contains the tooth 78a;

iii when the edge of the inclined portion 7% falls into a notch of the disc, the displacement of this edge does not depend on the depth of the notch but is equal to the difference of the spacing between the toothed track and the smooth track and the height of tooth 780. This displacement has a constant value regardless of the shape of the notch. Accordingly, provided the notch has a sufficiently large depth, the contact between the edge of tooth 73a and blade 73 exactly occurs in the very radial plane passing through the leading edge of the notch.

I claim:

1. An automatic dialling device associated with a dial telephone comprising a rotor, means for driving said rotor for one turn, a plurality of cam discs, each of said cam discs having a toothed track with rectangular notches indexed in its periphery and a smooth track having a diameter slightly smaller than the toothed track and adjacent thereto and accurately coaxial therewith, first blades and second read-out blades, each first blade resting on the smooth track and each second read-out blade terminating in a inclined portion provided with a toothed extension having a width lesser than the blade width, the edge of the inclined portion of said second blade engaging the notchesof the toothed track. in the radial plane passin through the contact point of the first blade and smooti trac and t e edge of the tooth extension resting on the first blade in the said radial plane when the edge of the inclined portion falls into a notch, means for detachably securing said cam discs to said rotor, a plurality of parallel selecting levers cooperating with the second read-out blades to disengage the same from the associated toothed track and terminating in a beak, a latch rod having therein a longitudinal slot adapted to engage the lever beaks, a switch for substituting the contact between the first and second blades for the dial contact of the telephone associated with the automatic dialling device and a member actuated by the latch rod for controlling said switch.

2. An automatic dialling device as set forth in claim i, in which each cam disc comprises a toothed track with rectangular notches indexed in a sectoral portion of its periphery and a pin located in the lateral face of the cam disc substantially in the radial plane limiting said sectoral portion, said pin cooperating with the selecting lever to disengage the same from the latch rod.

3. An automatic dialling device for dial telephones comprising a rotor, means for driving said rotor for one turn, a plurality of cam-discs, each of said cam-discs having a toothed track with rectangular notches indexed in its periphery and a smooth track having a slightly smaller diameter than the toothed track and being adjacent thereto and coaxial therewith, a plurality of first blades in a number equal to that of said cam-discs which are substantially parallel to each other, a plurality of second blades for read-out in a number equal to that of said cam-discs which are substantially parallel to each other and to said first blades, each first blade resting on the smooth track of a different one of said cam-discs and each second read-out blade bearing on the toothed track of a different one of sad cam-discs and terminating in an inclined portion provided with a substantially radial tooth extension having a width less than the read-out blade width, the edge of he inclined portion of said second blade engaging the notches of the toothed track in the radial plane passing through the contact point of the first blade and the smooth track and the edge of the tooth extension resting on the first blade in said radial plane when the edge of the inclined portion falls into a notch, means for detachably securing said cam-discs to said rotor and means for selecting one cam-discs to said rotor and means for selecting one cam-disc while inhibiting the others, inwhich said selecting and inhibiting means comprises pushbuttons respectively associated with the cam-discs, a plurality of parallel selecting levers actuated by said pushbuttons and cooperating with the read-out blades to disengage the same from the associated toothed track, said levers being terminated in a beak, and a rotatable latch rod having therein a longitudinal slot adapted to engage the lever beaks, whereby the operation of a lever causes the engagement of the lever beak into the slot and the rotation of the rod thereby preventing the other lever beaks to engage the slot. 

1. An automatic dialling device associated with a dial telephone comprising a rotor, means for driving said rotor for one turn, a plurality of cam discs, each of said cam discs having a toothed track with rectangular notches indexed in its periphery and a smooth track having a diameter slightly smaller than the toothed track and adjacent thereto and accurately coaxial therewith, first blades and second read-out blades, each first blade resting on the smooth track and each second read-Out blade terminating in a inclined portion provided with a toothed extension having a width lesser than the blade width, the edge of the inclined portion of said second blade engaging the notches of the toothed track in the radial plane passing through the contact point of the first blade and smooth track and the edge of the tooth extension resting on the first blade in the said radial plane when the edge of the inclined portion falls into a notch, means for detachably securing said cam discs to said rotor, a plurality of parallel selecting levers cooperating with the second read-out blades to disengage the same from the associated toothed track and terminating in a beak, a latch rod having therein a longitudinal slot adapted to engage the lever beaks, a switch for substituting the contact between the first and second blades for the dial contact of the telephone associated with the automatic dialling device and a member actuated by the latch rod for controlling said switch.
 2. An automatic dialling device as set forth in claim 1, in which each cam disc comprises a toothed track with rectangular notches indexed in a sectoral portion of its periphery and a pin located in the lateral face of the cam disc substantially in the radial plane limiting said sectoral portion, said pin cooperating with the selecting lever to disengage the same from the latch rod.
 3. An automatic dialling device for dial telephones comprising a rotor, means for driving said rotor for one turn, a plurality of cam-discs, each of said cam-discs having a toothed track with rectangular notches indexed in its periphery and a smooth track having a slightly smaller diameter than the toothed track and being adjacent thereto and coaxial therewith, a plurality of first blades in a number equal to that of said cam-discs which are substantially parallel to each other, a plurality of second blades for read-out in a number equal to that of said cam-discs which are substantially parallel to each other and to said first blades, each first blade resting on the smooth track of a different one of said cam-discs and each second read-out blade bearing on the toothed track of a different one of sad cam-discs and terminating in an inclined portion provided with a substantially radial tooth extension having a width less than the read-out blade width, the edge of he inclined portion of said second blade engaging the notches of the toothed track in the radial plane passing through the contact point of the first blade and the smooth track and the edge of the tooth extension resting on the first blade in said radial plane when the edge of the inclined portion falls into a notch, means for detachably securing said cam-discs to said rotor and means for selecting one cam-discs to said rotor and means for selecting one cam-disc while inhibiting the others, in which said selecting and inhibiting means comprises pushbuttons respectively associated with the cam-discs, a plurality of parallel selecting levers actuated by said pushbuttons and cooperating with the read-out blades to disengage the same from the associated toothed track, said levers being terminated in a beak, and a rotatable latch rod having therein a longitudinal slot adapted to engage the lever beaks, whereby the operation of a lever causes the engagement of the lever beak into the slot and the rotation of the rod thereby preventing the other lever beaks to engage the slot. 